Methods and apparatuses for data transmission in a wireless communication system

ABSTRACT

Embodiments of the present disclosure relate to downlink/uplink data transmission in a wireless communication system. In an embodiment of the present disclosure, there is provided a method for downlink data transmission in a wireless communication system which comprises transmitting an indication for a new-type reference signal to a user equipment, wherein the new-type reference signal has an identical location in frequency domain to a legacy reference signal; and transmitting the new-type reference signal and the legacy reference signal to the user equipment for using in channel estimation. In a case of more than one antenna port, the new-type reference signal may be designed to have a different location in time domain from a legacy reference signal to avoid interference to other antenna ports. With embodiments of the present disclosure, it is possible to perform a channel estimation based on both the legacy reference signal and the new-type reference signal to achieve a higher accuracy of channel estimation, and thus a UE with a low SNR may be also used in LTE networks.

FIELD OF THE INVENTION

Embodiments of the present disclosure generally relate to wirelesscommunication techniques and more particularly relate to a method andapparatus for downlink data transmission in a wireless communicationsystem and a method and apparatus for uplink data transmission in awireless communication system.

BACKGROUND OF THE INVENTION

With the constant increase of mobile data services, the 3rd GenerationPartnership Project (3GPP) organization has developed long-termevolution (LTE) specifications and LTE-Advanced (LTE-A) specifications.As the next generation cellular communication standard, an LTE orLTE-Advance system can operate in both Frequency Division Duplex (FDD)mode and Time Division Duplex (TDD) mode.

Machine-to-Machine (M2M) communication, which may also be called asMachine-Type Communications (MTC), is an emerging communication pattern.It refers to communication between computer, embedded processors, smartsensors, actuators and mobiles devices without or with only limitedhuman intervention and it is quite advantageous in many applicationssuch as sensing in extreme or hazard environment. Generally, many of MTCUEs are targeting low-end applications (low average revenue per user,and low data rate) that can be handled adequately by GSM/GPRS and thusthey may be implemented at low cost.

As LTE deployments evolve, it is desirable to reduce the cost of overallnetwork maintenance by minimizing the number of Radio AccessTechnologies (RATs). However, there are deployed more and more MTC UEsin the field, which increases reliance on GSM/GPRS networks, and thuscost for operating these networks are increased. Hence, it will be verybeneficial if low-end MTC UEs may be migrated from GSM/GPRS to LTENetworks.

It is known that in LTE releases 8 to 11, data transmission is designedfor medium or high SNR (SNR>−5 dB), but SNR of MTC UE could be as low as−25.3 dB. Accordingly, it is rather challenging to support MTC UEs incurrent Available LTE release.

FIG. 1A illustrates a mapping of downlink reference signals (normalcyclic prefix) as proposed in 3GPP TS 36.211. As illustrated, there areshown mappings of downlink cell specific reference signals (CRS) for oneantenna port, two antenna ports and four antenna ports. In this figure,each block represents a resource element (RE), and in order to preventthe interference between these ports, the resource elements which areused in one antenna port are not used for transmission in anotherantenna port, and vice versa. FIG. 1B schematically illustrates CRSconfiguration based on Rel. 8, which is specified in 3GPP TS36.211. Asillustrated, in step S101, evolved Node B (eNB) sends antennaPortsCountrepresenting the number of cell specific antenna ports to user equipment(UE) by Radio Resource Control (RRC) signalling. Then at step S102, theeNB sends CRS in corresponding antenna ports to the UE. The UE receivesthe CRS in an antenna port as indicated by antennaPortsCount andestimates channel based on the received CRS as step S103. Afterwards,the UE will carry out detection based on channel estimation results.However, as mentioned hereinabove, the illustrated CRS pattern isdesigned of medium and high SNR, and thus they can not be applied to MTCbecause it might bring out very low channel estimation accuracy.

Regarding the MTC UE migration, the 3GPP has started a study item tostudy a possibility to support MTC UEs in a low SNR region. InR1-130237, there was proposed to use demodulation reference signals(DMRS) configuration in LTE release 10 for MTC and suggest applyingpower boosting. FIG. 2A illustrates mapping of UE-specific referencesignals in antenna ports 7, 8, 9 and 10 (normal cyclic prefix) and FIG.2B illustrates DMRS configuration based on Rel. 10 (3GPP TS 36.211 & TS36. 331). As illustrated in FIG. 2A, antenna ports 7 and 8 have anidentical mapping and antenna port 9 and 10 also have an identicalmapping. This means that for MTC, it may only use one of antenna ports 7and 8 and one of antenna ports 9 and 10 to avoid interference betweenports. In FIG. 2B, antenna ports 7 and 9 are used. The operations asillustrated in FIG. 2B are substantially similar to that in FIG. 1Bexcept that the eNB sends transmission mode-r10 to the UE instead ofantennaPortsCount and the eNB send DMRS to the UE instead of CRS. Thus,like the CRS in Rel. 8, the DMRS configuration is still not suitable forMTC with a low SNR.

Therefore, there is a need for a new solution of data transmission in awireless for improving accuracy of channel estimation in a low SNRcommunication such as MTC.

SUMMARY OF THE INVENTION

In view of the foregoing, the present disclosure provides a new solutionfor data transmission in a wireless communication system so as to solveor at least partially mitigate at least a part of problems in the priorart.

According to a first aspect of the present disclosure, there is provideda method for downlink data transmission in a wireless communicationsystem. The method may comprise transmitting an indication for anew-type reference signal to a user equipment, wherein the new-typereference signal may be designed to have an identical location infrequency domain to a legacy reference signal; and transmitting thenew-type reference signal and the legacy reference signal to the userequipment for using in channel estimation.

In an embodiment of the present disclosure, the new-type referencesignal may be designed to have a different location in time domain fromthe legacy reference signal.

In another further embodiment of the present disclosure, the method mayfurther comprise determining a transmission repetition number for theuser equipment based on signal to noise ratio; and transmitting thetransmission repetition number to the user equipment.

In a further embodiment of the present disclosure, the method mayfurther comprise transmitting a power boosting parameter to the userequipment; and wherein the new-type reference signal is transmitted at aboosted power indicated by the power boosting parameter.

In a yet embodiment of the present disclosure, the new-type referencesignal may be transmitted when a physical downlink shared channelresource is scheduled for the user equipment.

In a still embodiment of the present disclosure, the legacy referencesignal may comprise any one of a cell specific reference signal and ademodulation reference signal.

In a still further embodiment of the present disclosure, the method isperformed in response to a coverage enhancement indication for the userequipment.

In a yet further embodiment of the present disclosure, sending to theuser equipment an antenna ports count indicating an antenna port numberfor transmitting the new-type reference signal and the legacy referencesignal.

According to a second aspect of the present disclosure, there is alsoprovided method for downlink data transmission in a wirelesscommunication system, comprising: receiving an indication for a new-typereference signal, wherein the new-type reference signal has an identicallocation in frequency domain to a legacy reference signal; receiving thenew-type reference signal and the legacy reference signal according tothe indication; and performing channel estimation based on both thenew-type reference signal and the legacy reference signal.

According to a third aspect of the present disclosure, there is furtherprovided an apparatus for downlink data transmission in a wirelesscommunication system. The apparatus may comprise an indicationtransmission unit, configured to transmit an indication for a new-typereference signal to a user equipment, wherein the new-type referencesignal has an identical location in frequency domain to a legacyreference signal; and a reference signal transmission unit configured totransmit the new-type reference signal and the legacy reference signalto the user equipment for using in channel estimation.

According to a fourth aspect of the present disclosure, there is furtherprovided an apparatus for downlink data transmission in a wirelesscommunication system. The apparatus may comprise an indication receivingunit configured to receive an indication for a new-type referencesignal, wherein the new-type reference signal has an identical locationin frequency domain to a legacy reference signal; a reference signalreceiving unit configured to receive the new-type reference signal andthe legacy reference signal in according to the indication; and achannel estimation unit configured to perform channel estimation basedon both the new-type reference signal and the legacy reference signal.

According to a fifth aspect of the present disclosure, there is provideda method for uplink data transmission in a wireless communicationsystem. The method may comprise transmitting an indication for anew-type reference signal to a user equipment, wherein the new-typereference signal has an identical location in frequency domain to alegacy reference signal; receiving the new-type reference signal and thelegacy reference signal from the user equipment; and performing channelestimation based on both the new-type reference signal and the legacyreference signal.

According to a sixth aspect of the present disclosure, there is providedanother method for uplink data transmission in a wireless communicationsystem. The method may comprise receiving an indication for a new-typereference signal from a base station, wherein the new-type referencesignal has an identical location in frequency domain to a legacyreference signal; and transmitting the new-type reference signal and thelegacy reference signal to the base station for using in channelestimation.

According to a seventh aspect of the present disclosure, there isprovided an apparatus for uplink data transmission in a wirelesscommunication system. The apparatus may comprise an indicationtransmission unit configured to transmit an indication for a new-typereference signal to a user equipment, wherein the new-type referencesignal has an identical location in frequency domain to a legacyreference signal; a reference signal receiving unit configured toreceive the new-type reference signal and the legacy reference signalfrom the user equipment; and a channel estimation unit configured toperform channel estimation based on both the new-type reference signaland the legacy reference signal.

According to an eighth aspect of the present disclosure, there isprovided another apparatus for uplink data transmission in a wirelesscommunication system. The apparatus may comprise indication receivingunit configured to receive an indication for a new-type reference signalfrom a base station, wherein the new-type reference signal has anidentical location in frequency domain to a legacy reference signal; anda reference signal transmission unit configured to transmit the new-typereference signal and the legacy reference signal to the base station forusing in channel estimation.

According to a ninth aspect of the present disclosure, there is furtherprovided, a computer-readable storage media with computer program codeembodied thereon, the computer program code configured to, whenexecuted, cause an apparatus to perform actions in the method accordingto any embodiment in any one of the first, second, fifth and sixthaspects.

According to a tenth aspect of the present disclosure, there is provideda computer program product comprising a computer-readable storage mediaaccording to the ninth aspect.

In embodiments of the present disclosure, there is provided a datatransmission solution in wireless communication. With embodiments of thepresent disclosure, it is possible performed channel estimation bycombining both CRS and the new-type reference signal as proposed in thepresent disclosure and thus it may improve the accuracy of channelestimation. Accordingly, it may support UE with a low SNR in LTEnetworks which reduce reliance on the older communication networks suchas GSM/GPRS networks.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present disclosure will become moreapparent through detailed explanation on the embodiments as illustratedin the embodiments with reference to the accompanying drawings,throughout which like reference numbers represent same or similarcomponents and wherein:

FIG. 1A schematically illustrates a mapping of downlink referencesignals (normal cyclic prefix) in Rel. 8;

FIG. 1B schematically illustrates CRS configuration based Rel. 8;

FIG. 2A schematically illustrates a mapping of UE-specific referencesignals, antenna ports 7, 8, 9 and 10 (normal cyclic prefix) asspecified in Rel. 10;

FIG. 2B schematically illustrates DMRS configuration based Rel. 10;

FIG. 3A schematically illustrates a flowchart of a method for downlinkdata transmission at an eNB in a wireless communication system accordingto an embodiment of the present disclosure;

FIG. 3B schematically illustrates a flowchart of a method for downlinkdata transmission at a UE in a wireless communication system accordingto an embodiment of the present disclosure;

FIG. 4A schematically illustrates a flowchart of a method for uplinkdata transmission at an eNB in a wireless communication system accordingto an embodiment of the present disclosure;

FIG. 4B schematically illustrates a flowchart of a method for uplinkdata transmission at a UE in a wireless communication system accordingto an embodiment of the present disclosure;

FIG. 5A schematically illustrates exemplary downlink MTCRS patterns forMTC with one antenna port and two antenna ports respectively accordingto an embodiment of the present disclosure;

FIG. 5B schematically illustrates an exemplary downlink MTCRS patternfor MTC with four antenna ports according to an embodiment of thepresent disclosure;

FIG. 6 schematically illustrates a flow chart of a method for referencesignal configuration according to an embodiment of the presentdisclosure;

FIG. 7 schematically illustrates another exemplary downlink MTCRSpattern for MTC with two antennae according to an embodiment of thepresent disclosure;

FIG. 8 schematically illustrates a further exemplary downlink MTCRSpattern for MTC according to an embodiment of the present disclosure;

FIG. 9 schematically illustrates an exemplary uplink MTCRS pattern forMTC according to an embodiment of the present disclosure;

FIG. 10A schematically illustrates a flow chart of a method forconfiguring UE for coverage enhancement in uplink transmission accordingto an embodiment of the present disclosure;

FIG. 10B schematically illustrates a flow chart of a method for channelestimation at an eNB for coverage enhancement in uplink transmissionaccording to an embodiment of the present disclosure;

FIG. 11 schematically illustrates a block diagram of an apparatus fordownlink data transmission at an eNB in a wireless communication systemaccording to an embodiment of the present disclosure;

FIG. 12 schematically illustrates a block diagram of an apparatus fordownlink data transmission at a UE in a wireless communication systemaccording to an embodiment of the present disclosure;

FIG. 13 schematically illustrates a block diagram of an apparatus foruplink data transmission at an eNB in a wireless communication systemaccording to an embodiment of the present disclosure;

FIG. 14 schematically illustrates a block diagram of an apparatus foruplink data transmission at a UE in a wireless communication systemaccording to an embodiment of the present disclosure;

FIGS. 15A and 15B illustrate simulation results on performance of theredifferent schemes with 0 dB power offset and 3 dB power offset; and

FIGS. 16A and 16B illustrate simulation results on performance of theredifferent schemes with 0 Hz frequency offset and 100 Hz frequencyoffset.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, a method and apparatus for data transmission in a wirelesscommunication system will be described in details through embodimentswith reference to the accompanying drawings. It should be appreciatedthat these embodiments are presented only to enable those skilled in theart to better understand and implement the present disclosure, notintended to limit the scope of the present disclosure in any manner.

In the accompanying drawings, various embodiments of the presentdisclosure are illustrated in block diagrams, flow charts and otherdiagrams. Each block in the flowcharts or block may represent a module,a program, or a part of code, which contains one or more executableinstructions for performing specified logic functions and indispensibleblock is illustrated in a dotted line. Besides, although these blocksare illustrated in particular sequences for performing the steps of themethods, as a matter of fact, they may not necessarily be performedstrictly according to the illustrated sequence. For example, they mightbe performed in reverse sequence or simultaneously, which is dependenton natures of respective operations. It should also be noted that blockdiagrams and/or each block in the flowcharts and a combination ofthereof may be implemented by a dedicated hardware-based system forperforming specified functions/operations or by a combination ofdedicated hardware and computer instructions.

Generally, all terms used in the claims are to be interpreted accordingto their ordinary meaning in the technical field, unless explicitlydefined otherwise herein. All references to “a/an/the/said [element,device, component, means, step, etc]” are to be interpreted openly asreferring to at least one instance of said element, device, component,means, unit, step, etc., without excluding a plurality of such devices,components, means, units, steps, etc., unless explicitly statedotherwise. Besides, the indefinite article “a/an” as used herein doesnot exclude a plurality of such steps, units, modules, devices, andobjects, and etc.

Additionally, in a context of the present disclosure, a user equipment(UE) may refer to a terminal, a Mobile Terminal (MT), a SubscriberStation (SS), a Portable Subscriber Station (PSS), Mobile Station (MS),or an Access Terminal (AT), and some or all of the functions of the UE,the terminal, the MT, the SS, the PSS, the MS, or the AT may beincluded. Furthermore, in the context of the present disclosure, theterm “BS” may represent, e.g., a node B (NodeB or NB), an evolved NodeB(eNodeB or eNB), a radio header (RH), a remote radio head (RRH), arelay, or a low power node such as a femto, a pico, and so on.

For a better understanding of the present disclosure, the followingdescription will be made to embodiments of the present disclosure bytaking MTC as an example. However, as can be appreciated by thoseskilled in the art, the present invention could be applied to any othersuitable communication with a low SNR.

First, reference will made to FIG. 3A to describe a method for downlinkdata transmission at an eNB in a wireless communication system accordingto an embodiment of the present disclosure.

As illustrated, first at step A301, the eNB may transmit an indicationfor a new-type reference signal to a user equipment.

As mentioned in background, CRS pattern in Rel. 8 is designed for mediumor high SNR while in DMRS pattern, only a part of ports can be used,thus they are not suitable for communication with a low SNR such as MTC.Moreover, it is impossible to use the two reference signal patternstogether because they can not be aligned with each other in frequencydomain.

In view of this, in the present disclosure, there is proposed a new-typereference signal, which may be called as MTCRS. The main idea is toincrease the density of reference symbols in resource elements. In anembodiment of the present invention, the new-type reference signal maybe designed so that the new-type reference signal has an identicallocation in frequency domain to a legacy reference signal such as CRS orDMRS. That is to say, the new-type reference signal is shifting in asimilar way to the legacy reference signal. In such as way, not only thedensity of reference symbols is increased, but also the newly addedreference symbols may be used to perform channel estimation togetherwith the legacy reference signal. This means more resource elements maybe use to transmit reference symbols while it may be compatible inexisting LTE networks.

Additionally, when more than one antenna port is used to transmitreference symbols, the new-type reference may be further designed sothat it has a different location in time domain from the legacyreference signal so as to avoid interference to other antenna ports,i.e., the legacy reference signal and the new-type reference will bestaggered in time domain. More exemplary patterns of MTCRS will bedescribed hereinafter.

The eNB may transmit the indication by, for example, an Radio ResourceControl (RRC) signalling or any other suitable signalling such asphysical layer signalling. Besides, as usual, before transmitting theindication, the eNB may first send antennaPortsCount to all UEs that itserves by (RRC) signaling; however, the antennaPortsCount will representthe antenna port numbers for both the legacy reference signal and theantenna port number for the new-type reference signal MTCRS. Forexample, the RRC configuration containing antennaPortsCount may betransmitted to the UE, wherein it may also include a transmission mode:transmissionMode-r10 to inform the UE the transmission mode that is usedby the eNB.

Then at step A302, the eNB sends both the legacy reference signal suchas CRS or DMRS and the new-type reference signal MTCRS to the UE forusing in the channel estimation. In such a way, the UE may use both thelegacy reference signal and the new-type reference signal MTCRS toperform jointly a channel estimation.

Besides, at step A303, the eNB may determine a transmission repetitionnumber for the UE based on signal to noise ratio. Specifically, the eNBmay first estimate the SNR for the UE, then by looking up a pre-definedrelationship curve between the repetition number and SNR, it may obtaina repetition number corresponding to the estimated SNR and this obtainedrepetition number may be estimated as the repetition number N for theUE.

After that, the eNB may transmit at step A304 the transmissionrepetition number N to the UE, so that UE can learn the transmissionrepetition number and demodulate the signals based thereon. That is tosay the UE may learn the right time for beginning to demodulate signal.Therefore, the UE will not perform demodulation until it has receivedpackets with an amount equal to the transmission repetition number, orin other words, the UE keeps waiting before enough packets arrive.

Additionally, it may additionally apply power boosting to increase theintensity of reference symbols, thereby achieving a further convergeenhancement. To do this, the eNB may determine a power boostingparameter which indicates the boosted power for transmit the new-typereference signal MTCRS and the power boosting parameter may betransmitted to the UE at step A304 so that the UE can know the powerboosting parameter. In such a way, the UE may use the information aboutthe power boosting parameter in channel estimation. For example, thepower boosting parameter ρ_(D) may indicate energy per resource element(EPRE) to the CRS EPER. Usually, the UE knows the CRS EPRE, and thus thepower of MTCRS may be determined based on the power of CRS and the powerboosting parameters ρ_(D). Additionally, the power boosting parametermay be also defined relative the physical downlink shared channelresource (PDSCH).

In some embodiments of the present disclosure, the new-type referencesignal may be sent in a UE-specific way, i.e., the new-type referencesignal may be sent only when the PDSCH is scheduled for the userequipment. Therefore, it is possible to configure a UE individually interms of the new-type reference signal. If the legacy reference signalmay also be sent in a UE-specific way (for example for DMRS), the legacyreference signal may also be transmitted only when the PDSCH isscheduled for the user equipment.

Additionally, the method may be performed only when the UE needscoverage enhancement. Therefore, in embodiments of the presentinvention, the method is performed in response to a coverage enhancementindication for the user equipment. When the UE does not require coverageenhancement indication, the method may not be performed.

Furthermore, as mentioned hereinabove, the eNB may send the antenna portnumber to the UE to inform the antenna port on which the new-typereference signal is transmitted. For example, the eNB may send aparameter antennaPortsCount to the UE, which indicates antenna portnumbers for transmitting the new-type reference signal and the legacyreference signal. In such way, the UE may learn antenna port informationso that it can obtain the new-type reference signal therefrom. However,it may also be feasible without sending the antenna port number by usingpre-determined antenna ports which are know to both the eNB and the UE.

Hereinafter, a method for downlink data transmission at a UE in awireless communication system according to an embodiment of the presentdisclosure will be described with reference to FIG. 3B.

As illustrated, in step B301, the UE will receive an indication for thenew-type reference signal from the base station. From this indication,the UE may know that, in addition to the legacy reference signal such asCRS or DMRS, a new-type reference signal MTCRS will be transmitted fromthe base station. Hence, at step B302 the UE will receive, according thereceived indication, both the new-type reference signal and the legacyreference signal. The UE may receive these reference signals on antennaports for example indicated by parameter antennaPortsCount which is alsotransmitted from the eNB.

As described previously, the new-type reference signal is a referencesignal different from the legacy reference signal, and it may bedesigned so that the new-type reference signal has an identical locationin frequency domain as a legacy reference signal such as CRS or DMRS.Additionally, when more than one antenna port is used, the new-typereference may be further designed so that it has a different location intime domain from a legacy reference signal, i.e., the legacy referencesignal and the new-type reference will be staggered in time domain. Dueto such a special design for the new-type signal, the UE may combine thenew-type reference signal and the legacy reference signal together toperform channel estimation at step B303.

Additionally, the UE may further receive a transmission repetitionnumber from the eNB at step B304, and thus the UE can demodulate signalsbased on the transmission repetition number. For example, only when ithas received packets with an amount equal to the transmission repetitionnumber, the UE will start signal demodulation.

Likely that at the eNB, the method as illustrated in FIG. 3B may also beperformed when the UE requires coverage enhancement.

Besides, in the present disclosure, there are also provided methods foruplink data transmission in a wireless communication system, which willbe described with reference to FIGS. 4A and 4B.

FIG. 4A schematically illustrate a flowchart of a method for uplink datatransmission at an eNB in a wireless communication system according toan embodiment of the present disclosure. As illustrated in FIG. 4A,first at step A401, the eNB transmits an indication for a new-typereference signal to a user equipment. As mentioned hereinbefore, thenew-type reference signal may be designed so that the new-type referencesignal has an identical location in frequency domain as a legacyreference signal such as DMRS. The new-type reference signal may furtherhave different location in time domain, i.e., they are staggered in timedomain. An exemplary MTCRS pattern for MTC will be describedhereinafter.

The indication may also be transmitted by for example, RRC signalling orany other suitable signalling such as physical layer signalling.Furthermore, the eNB may send the antenna port number to the UE toinform the antenna port on which the reference signals are transmitted.For example, the eNB may send a parameter antennaPortsCount to the UE,which indicates antenna port numbers for transmitting the new-typereference signal and the legacy reference signal. In such way, the UEmay learn antenna port information so that it can transmit the referencesignals thereon.

Next, at step A402, the eNB may receive the new-type reference signaland the legacy reference signal from the UE on the antenna ports forexample indicated by the parameter antennaPortsCount. Afterwards, atstep A403, the eNB may perform channel estimation based on the receivednew-type reference signal and the received legacy reference signal.

Additionally, at step A404, the eNB may further determine a transmissionrepetition number for the UE based on signal to noise ratio and transmitthe transmission repetition number to the UE, so that UE can learn thetransmission repetition number and demodulate the signals when it hasreceived packets with an amount equal to the transmission repetitionnumber.

Besides, the method may be also performed only when the UE needscoverage enhancement. Therefore, in embodiments of the presentinvention, the method is performed in response to a coverage enhancementindication for the user equipment while the method may be not performedwhen the UE does not require coverage enhancement indication.

FIG. 4B schematically illustrates a flowchart of a method for uplinkdata transmission at a UE in a wireless communication system accordingto embodiments of the present disclosure. As illustrated in FIG. 4B,first at step B401, the UE receives an indication for the new-typereference signal MTCRS. From this indication, the UE may know that, inaddition to the legacy reference signal such as DMRS, it should transmita new-type reference signal MTCRS to the base station. Then at stepB402, the UE will transmit both the legacy reference signal and anew-type reference signal MTCRS to the eNB for using in channelestimation. The new-type reference signal may be transmitted in aUE-specific way. For example, it may be transmitted only when a physicaluplink shared channel resource (PUSCH) is scheduled for the userequipment. Similarly, if the legacy reference signal may also be sent ina UE-specific way (for example for DMRS), the legacy reference signalmay also be transmitted only when the PUSCH is scheduled for the userequipment.

Additionally, the UE may also receive a transmission repetition numberfrom the base station at step B403. In such a way, the UE may transmitsignals based on the transmission repetition number. Moreover, themethod as illustrated in FIG. 4B may be performed in response to acoverage enhancement indication for the user equipment. In other words,the method will be performed only when the UE requires coverageenhancement.

Besides, before transmitting the reference signals, the UE may receivefrom the eNB an antenna ports count that indicates an antenna portnumber for transmitting the new-type reference signal and the legacyreference signal so that the UE can learn use which antenna ports to usefor transmitting the reference signals. However, it should beappreciated that it may also be feasible to use pre-determined antennaports known to both the eNB and the UE.

Hereinbefore, some embodiments of the present disclosure have beendescribed with reference to FIGS. 3A, 3B, 4A and 4B, and in thefollowing some specific examples will be described to enable the skilledin the art to well understand the idea of the present invention.

FIGS. 5A and 5B schematically illustrate exemplary downlink MTCRSpatterns for MTC with one antenna port, two antenna ports and fourantenna ports respectively, wherein reference signal ports 23 and 24 arenewly added ports.

For one antenna port, it may be seen that besides original resourcereference symbols R₀ which are shown in a dark background, there isfurther provided a new reference symbol R₂₃ which will be alsotransmitted on antenna port 1. It is clear that all reference symbolsR₂₃ have similar locations to the original reference symbols R₀ infrequency domain i.e., they are shifting in a similar way to thereference symbols R₀. Except the first three time slots for publiccontrol channel, reference symbols R₂₃ may occupy four subcarriers inall time slots as long as these subcarriers are not occupied byreference symbols R₀. However, it may be appreciated that MTCRS may bearranged in other ways, such as reference symbols R₂₃ may occupy onlypart of these subcarriers and/or part of the time slots. Additionally,it may be also appreciated that it is also possible to arrange referencesymbols R₂₃ in the first three time slots.

From FIG. 5A, it may also be seen that, for two antenna ports, there arenewly added two reference signal ports 23 and 24 instead of only oneantenna port 23. All reference symbols R₂₃ and R₂₄ have similarlocations to the original reference symbols R₀ and R₁ in frequencydomain i.e., they are shifting in a similar way to the reference symbolsR₀ and R₁, respectively. Except the first three time slots and the timeslots already occupied by reference symbols R₀ and R₁, reference symbolsR₂₃ and R₂₄ occupies all of the remaining eight time slots. And it mayalso be clear that in each time slot that reference symbols R₂₃ and R₂₄occupy, reference symbols R₂₃ and R₂₄ have different locations infrequency domain so as to avoid interference with each other. However,it should be noted that many other MTCRS patterns are possible, forexample, reference symbols R₂₃ and R₂₄ may occupy part of the eightremaining time slots (for example four or six of the remaining timeslots), occupy part of possible subcarriers in a time slot, etc.

FIG. 5B schematically illustrates an exemplary downlink MTCRS patternfor MTC with four antenna ports. As is clear from FIG. 5B, the antennaport 0 and the antenna port 1 have generally similar pattern as thoseillustrated in FIG. 5A for two antenna ports, but in order to avoidinterference, in antenna ports 0 and 1, those time slots occupied byreference symbols R₂ and R₃ are forbidden to use by reference symbolsR₂₃ and R₂₄, and in antenna ports 2 and 3, subcarriers corresponding tothose reference symbols R₂₃ and R₂₄ have been forbidden to use too.

FIG. 6 illustrates a flow chart of a method for reference signalsconfiguration according to an embodiment of the present disclosurewherein operations specific to the present disclosure are highlighted byblocks in bold lines.

As illustrated in FIG. 6, at step S601, the eNB sends a parameterantennaPortsCount to all UEs by RRC signaling as usual. The parameterantennaPortsCount contains information for indicating antenna ports fortransmitting reference signals, for example antenna port 0, antennaports 1 and 2, or antenna ports 0 to 3, etc. Then at step S602, eNB mayestimate the transmission repetition number for the UE. Specifically,the eNB first estimate SNR of the UE and then it may determine therepetition number N based on the estimated SNR and a predeterminedrelationship curve of the SNR and the repetition number. For example, bylooking up the predetermined relationship curve, it may find arepetition number corresponding to the estimated SNR, which may bedetermined as the transmission repetition number for the UE.

After that, at step S603, the eNB may determine whether the UE needscoverage enhancement. For example, if the estimated SNR is lower than apredetermined threshold, it may determine the UE needs coverageenhancement, or the UE belongs to a type of UE with a low SNR. If the UEdoes need coverage enhancement, then the procedure proceeds into stepS604, at which the eNB sends an enable MTCRS indication to the UE toindicate that the MTCRS will be used in addition to the traditionalreference signal such as CRS or DMRS. Additionally, the eNB may transmitto the UE the estimated repetition number N so that the UE may obtainthe repletion number for using in demodulation. In addition, the eNB mayalso send a boosting parameter ρ_(D) to the UE so that the UE can knowthe EPRE of MTCRS.

Then, the eNB may generate the MTCRS sequence. The MTCRS may begenerated in a same way as CRS in Section 6.10.1 of TS 36.211 but with adifferent mapping to resource elements. For the MTCRS patterns asillustrated and in FIG. 5A and FIG. 5B, the reference signal sequencer_(i,n,MTC)(m) may be mapped to complex-valued modulation symbolsa_(k,l,MTC) ^((p)) used as reference symbols for antenna port p in slotn_(s) according to the following equation:

a_(k, l, MTC)^((p)) = r_(l, n_(s), MTC)(m^(′)) whereink = 6 m + (v + v_(shift))mod 6;m = 0, 1, …  , 2 ⋅ N_(RB)^(DL) − 1; andm^(′) = n + N_(RB)^(max , DL) − N_(RB)^(DL) if  p = 1$l = \left\{ {{\begin{matrix}{3,4,5,6} & {{{if}\mspace{14mu} n_{s}{mod}\; 2} = 0} \\{0,1,2,3,4,5,6} & {{{if}\mspace{14mu} n_{s}\; {mod}\; 2} = 1}\end{matrix}v} = \left\{ {{\begin{matrix}0 & {{l = 3},4,5,{{6\mspace{14mu} {and}\mspace{14mu} n_{s}{mod}\; 2} = 0}} \\3 & {{l = 3},5,{{6\mspace{14mu} {and}\mspace{14mu} n_{s}\; {mod}\; 2} = 0}} \\0 & {{l = 1},2,3,4,5,{{6\mspace{14mu} {and}\mspace{14mu} n_{s}\; {mod}\; 2} = 1}} \\3 & {{l = 0},1,2,3,5,{{6\mspace{14mu} {and}\mspace{14mu} n_{s}\; {mod}\; 2} = 1}}\end{matrix}{if}\; p} = {{2l} = \left\{ {{\begin{matrix}{3,5,6} & {{{if}\mspace{14mu} n_{s}\; {mod}\; 2} = 0} \\{1,2,3,5,6} & {{{if}\mspace{14mu} n_{s}\; {mod}\; 2} = 1}\end{matrix}v} = \left\{ {{\begin{matrix}0 & {{{{if}\mspace{14mu} p} = {{0\mspace{14mu} {and}\mspace{14mu} l} = 3}},5} & {{{and}\mspace{14mu} n_{s}\; {mod}\; 2} = 0} \\3 & {{{if}\mspace{14mu} p} = {{0\mspace{14mu} {and}\mspace{14mu} l} = 6}} & {{{and}\mspace{14mu} n_{s}\; {mod}\; 2} = 0} \\0 & {{{{if}\mspace{14mu} p} = {{0\mspace{11mu} {and}\mspace{14mu} l} = 3}},5} & {{{and}\mspace{14mu} n_{s}\; {mod}\; 2} = 1} \\3 & {{{{if}\mspace{14mu} p} = {{0\mspace{14mu} {and}\mspace{14mu} l} = 1}},2,6} & {{{and}\mspace{14mu} n_{s}\; {mod}\; 2} = 1} \\0 & {{{{if}\mspace{14mu} p} = {{1\mspace{14mu} {and}\mspace{14mu} l} = 3}},5} & {{{and}\mspace{14mu} n_{s}\; {mod}\; 2} = 0} \\3 & {{{if}\mspace{14mu} p} = {{1\mspace{14mu} {and}\mspace{14mu} l} = 6}} & {{{and}\mspace{14mu} n_{s}\; {mod}\; 2} = 0} \\0 & {{{{if}\mspace{14mu} p} = {{1\mspace{14mu} {and}\mspace{14mu} l} = 3}},5} & {{{and}\mspace{14mu} n_{s}{mod}\; 2} = 1} \\3 & {{{{if}\mspace{14mu} p} = {{1\mspace{14mu} {and}\mspace{14mu} l} = 1}},2,6} & {{{and}\mspace{14mu} n_{s}\; {mod}\; 2} = 1}\end{matrix}{if}\mspace{14mu} p} = {{4l} = \left\{ {{\begin{matrix}{3,5,6} & {{{if}\mspace{14mu} n_{s}\; {mod}\; 2} = 0} \\{2,3,5,6} & {{{if}\mspace{14mu} n_{s}\; {mod}\; 2} = 1}\end{matrix}v} = \left\{ \begin{matrix}0 & {{{{if}\mspace{14mu} p} = {{0\mspace{14mu} {and}\mspace{14mu} l} = 3}},5} & {{{and}\mspace{14mu} n_{s}\; {mod}\; 2} = 0} \\3 & {{{if}\mspace{14mu} p} = {{0\mspace{14mu} {and}\mspace{14mu} l} = 6}} & {{{and}\mspace{14mu} n_{s}\; {mod}\; 2} = 0} \\0 & {{{{if}\mspace{14mu} p} = {{0\mspace{11mu} {and}\mspace{14mu} l} = 3}},5} & {{{and}\mspace{14mu} n_{s}\; {mod}\; 2} = 1} \\3 & {{{{if}\mspace{14mu} p} = {{0\mspace{14mu} {and}\mspace{14mu} l} = 2}},6} & {{{and}\mspace{14mu} n_{s}\; {mod}\; 2} = 1} \\0 & {{{{if}\mspace{14mu} p} = {{1\mspace{14mu} {and}\mspace{14mu} l} = 3}},5} & {{{and}\mspace{14mu} n_{s}\; {mod}\; 2} = 0} \\3 & {{{if}\mspace{14mu} p} = {{1\mspace{14mu} {and}\mspace{14mu} l} = 6}} & {{{and}\mspace{14mu} n_{s}\; {mod}\; 2} = 0} \\0 & {{{{if}\mspace{14mu} p} = {{1\mspace{14mu} {and}\mspace{14mu} l} = 3}},5} & {{{and}\mspace{14mu} n_{s}{mod}\; 2} = 1} \\3 & {{{{if}\mspace{14mu} p} = {{1\mspace{14mu} {and}\mspace{14mu} l} = 2}},6} & {{{and}\mspace{14mu} n_{s}\; {mod}\; 2} = 1}\end{matrix} \right.} \right.}} \right.} \right.}} \right.} \right.$

wherein k denotes an index of a resource element in a frequency domain,l denotes an index of a resource element in a time domain, n_(s) denotesan index of the time slots; p denotes the number of antenna ports fortransmitting reference signals; m denotes an index of the referencesymbols; m′ denotes the index of the generated sequence; v denotes thefrequency domain position of a reference signal and “mod” denotes a modoperation. In accordance with the given mapping, MTCRS sequencegeneration may be implemented in a similar way to that for the CRS.

Next, the eNB sends both the generated CRS and MTCRS to the UE at stepS605. The power setting of the MTCRS may be determined by the powerboosting parameter ρ_(D), i.e., the MTCRS will be transmitted at aboosted power indicated by the power boosting parameter ρ_(D). The MTCRSmay be sent in a UE-specific way, i.e., they may be sent only when thephysical downlink control channel is scheduled for the UE.

So the UE may obtain the CRS and MTCRS on one or more antenna portsindicated by antennaPortsCount according to the enable MTCRS indication.Thus, the UE may estimate channel based on both CRS and MTCRS at thesame time. Since there is additionally provided a MTCRS, the intensityof references symbols is increased which means more reference symbolsmay be to be transmitted at a time, thus the accuracy of channelestimation in a lower SNR may be improved.

On the other hand, if the UE does not require coverage enhancement, theprocedure may proceed into step 607 and eNB sends only CRS to the UE.Since the UE has received the RRC configuration, it knows the CRSconfiguration and thus it may estimate channel based on CRS pattern atstep S608. Then, at step S609, the UE may carry out detection based onchannel estimation results.

Beside, FIG. 7 schematically illustrates another exemplary downlinkMTCRS pattern for MTC with two antennae according to an embodiment ofthe present disclosure. As illustrated, reference symbols R₂₃ and R₂₄also have similar locations to the original reference symbols R₀ and R₁in frequency domain and in each time slot reference symbols R₂₃ and R₂₄have different locations in frequency domain so as to avoid interferencewith each other. However, different from MTCRS for two antenna ports asillustrated in FIG. 5A, reference symbols R₂₃ and R₂₄ are much sparserand they occupy only a half of the time slots that occupied by referencesymbols R23 and R24 as illustrated in FIG. 5A.

FIG. 8 also schematically illustrates another downlink MTCRS pattern forMTC according to an embodiment of the present disclosure. Different fromthose illustrated in FIGS. 5A and 5B, this MTCRS as illustrated in FIG.9 is based on DMRS instead of CRS in Rel. 8. As illustrated, there arenewly added reference signal ports 23 and 24 to for antenna port 7 and 9respectively. As is clear, all reference symbols R₂₃ and R₂₄ havesimilar locations in frequency domain to the original reference symbolsR₇ and R₉ respectively, i.e., they are shifting in a similar way to thereference symbols R₇ and R₉ respectively. Except the first three timeslots for public channel and the time slots occupied by referencesymbols R₀ and R₁, reference symbols R₂₃ and R₂₄ occupies a half of theremaining eight time slots even though they may also occupy more or evenall of these time slots. From the description of mapping to resourceelements regarding FIGS. 5A and 5B, the skilled in the art may learn themapping for the MTCRS as illustrated in FIG. 8 and thus no descriptionis elaborated herein. Additionally, for antenna ports 8 and 10, MTCRScan be arranged in a similar way.

FIG. 9 schematically illustrates an uplink MTCRS pattern for MTCaccording to an embodiment of the present disclosure. It is clear thatthe uplink MTCRS is based on DMRS in Rel. 10, wherein reference signalport 0 is a legacy port and reference signal port 23 is a new port asproposed in the present disclosure. As is shown, reference symbols R₂₃have similar locations to the legacy reference symbols R₀ in frequencydomain, and they occupy all subcarriers in two of the time slots notoccupied by reference symbols R₀ although they may occupy more or lesstime slots or part of the subcarriers in a time slot.

FIG. 10A schematically illustrates a flow chart of a method forconfiguring UE for coverage enhancement in uplink transmission accordingto an embodiment of the present disclosure. As illustrated, at stepS1001, the eNB sends a parameter antennaPortsCount to all UEs by forexample, a RRC signaling. The parameter antennaPortsCount containsinformation for indicating antenna ports for transmitting referencesignals, for example antenna port 0. Then at step S1002, the eNB mayestimate the transmission repetition number for a UE. Specifically, theeNB first estimates SNR of the UE and then it may determine therepetition number N based on the estimated SNR and a predeterminedrelationship curve of the SNR and the repetition number. For example, bylooking up the predetermined relationship curve with the estimated SNR,it may find a repetition number corresponding to the estimated SNR,which may be determined as the transmission repetition number for theUE.

After that, at step S1003, it may determine whether the UE needscoverage enhancement or not. For example, if the estimated SNR is lowerthan a predetermined threshold or the UE belongs to a type of UE with alow SNR, it may determine the UE needs coverage enhancement. If the UEneeds coverage enhancement, then the procedure proceeds into step S1004,in which the eNB sends an enable MTCRS indication to the UE to indicatethat the MTCRS will be used in addition to the traditional referencesignal such as DMRS. Additionally, the eNB may transmit to the UE theestimated repetition number N so that the UE may obtain the repletionnumber for transmitting signals. On the other hand, if the UE does notrequire coverage enhancement, the procedure ends.

FIG. 10B schematically illustrates a flow chart of a method for channelestimation at UE for coverage enhancement in uplink transmissionaccording to an embodiment of the present disclosure. As illustrated,the UE may first determine whether the UE needs coverage enhancement. Ifthe UE does need coverage enhancement, then the procedure proceeds intostep S1006, in which the UE sends both DMRS and MTCRS to the eNB. TheMTCRS sequence may be generated in a similar way to the DMRS but using adifferent mapping. The MTCRS may be sent in a UE-specific way, they maybe sent only when the physical uplink control channel is scheduled forthe UE.

Next, the eNB may receive DMRS and MTCRS and estimate the uplink channelbased on both DMRS and MTCRS at step S1007. On the other hand, if the UEdoes not require coverage enhancement, the procedure will proceed intostep S1008, i.e., the UE sends only DRMS to the eNB as usual. Then, asstep S1009, the eNB will estimate the uplink channel based on only thereceived DMRS. Finally, at Step S1010, the eNB will perform detectionbased on results of channel estimation.

Additionally, in the present disclosure, there is also providedapparatuses for downlink/uplink data transmission in a wirelesscommunication system. Next, reference will be made to FIGS. 11 to 14 todescribe the apparatuses as provided in the present disclosure.

FIG. 11 schematically illustrates an apparatus 1100 for downlink datatransmission at an eNB in a wireless communication system according toan embodiment of the present disclosure. It is clear from FIG. 11 thatthe apparatus 1100 may comprise an indication transmission unit 1110 anda reference signal transmission unit 1120. The indication transmissionunit 1110 may be configured to transmit an indication for a new-typereference signal to a user equipment, wherein the new-type referencesignal has an identical location in frequency domain to a legacyreference signal. The reference signal transmission unit 1120 may beconfigured to transmit the new-type reference signal and the legacyreference signal to the user equipment for using in channel estimation.

In an embodiment of the present disclosure, the new-type referencesignal may be further designed so that it has a different location intime domain from the legacy reference signal.

Additionally, the apparatus 1100 may further comprise a repetitionnumber determination unit 1130 and a repetition number transmission unit1140. The repetition number determination unit 1130 may be configured todetermine a transmission repetition number for the user equipment basedon signal to noise ratio. The repetition number transmission unit 1140may be configured to transmit the transmission repetition number to theuser equipment.

In another embodiment of the present disclosure, the reference signaltransmission unit 1120 may be further configured to transmit thenew-type reference signal when a physical downlink shared channelresource is scheduled for the user equipment.

FIG. 12 schematically illustrates an apparatus 1200 for downlink datatransmission at a UE in a wireless communication system according to anembodiment of the present disclosure. As illustrated, the apparatus 1200may comprise an indication receiving unit 1210, a reference signalreceiving unit 1220 and a channel estimation unit 1230. The indicationreceiving unit 1210 may be configured to receive an indication for anew-type reference signal, wherein the new-type reference signal has anidentical location in frequency domain to a legacy reference signal. Thereference signal receiving unit 1220 may be configured to receive thenew-type reference signal and the legacy reference signal in accordingto the indication. The channel estimation unit 1230 may be configured toperform channel estimation based on both the new-type reference signaland the legacy reference signal.

In an embodiment of the present disclosure, the new-type referencesignal may be designed to have a different location in time domain fromthe legacy reference signal.

Additionally, as illustrated, the apparatus 1200 may further comprise arepetition number receiving unit 1240 configured to receive atransmission repetition number so as to perform signal demodulationbased on the transmission repetition number.

Besides, FIG. 13 schematically illustrates an apparatus 1300 for uplinkdata transmission at an eNB in a wireless communication system accordingto an embodiment of the present disclosure. As illustrated, theapparatus 1300 may comprise an indication transmission unit 1310, areference signal receiving unit 1320 and a channel estimation unit 1330.The indication transmission unit 1310 may be configured to transmit anindication for a new-type reference signal to a user equipment, whereinthe new-type reference signal has an identical location in frequencydomain to a legacy reference signal. The reference signal receiving unit1320 may be configured to receive the new-type reference signal and thelegacy reference signal from the user equipment. The channel estimationunit 1330 may be configured to perform channel estimation based on boththe new-type reference signal and the legacy reference signal.

In an embodiment of the present disclosure, the new-type referencesignal has a different location in time domain from the legacy referencesignal.

In addition, as illustrated in FIG. 13, the apparatus 1300 may furthercomprise a repetition number determination unit 1340 and a repetitionnumber determination unit 1350. The repetition number determination unit1340 may be configured to determine a transmission repetition number forthe user equipment based on signal to noise ratio. The repetition numberdetermination unit 1350 may be configured to transmit the transmissionrepetition number to the user equipment.

FIG. 14 schematically illustrates an apparatus 1400 for uplink datatransmission at a UE in a wireless communication system according to anembodiment of the present disclosure. The apparatus 1400 may comprise anindication receiving unit 1410 and a reference signal transmission unit1420. The indication receiving unit 1410 may be configured to receive anindication for a new-type reference signal from a base station, whereinthe new-type reference signal has an identical location in frequencydomain to a legacy reference signal. The reference signal transmissionunit 1420 may be configured to transmit the new-type reference signaland the legacy reference signal to the base station for using in channelestimation.

In an embodiment of the present invention, the new-type reference signalmay have a different location in time domain from the legacy referencesignal.

Additionally, the apparatus 1400 may further comprise a repetitionnumber receiving unit 1430, which may be configured to receive atransmission repetition number from the base station so as to transmitsignals based thereon.

In another embodiment of the present disclosure, the reference signaltransmission unit 1420 is further configured to transmit the new-typereference signal when a physical uplink shared channel resource isscheduled for the user equipment.

It is noted that the apparatuses 1100 to 1400 may be configured toimplement functionalities as described with reference to FIG. 3A to FIG.4B. Therefore, for details about the operations of modules in theseapparatus, one may refer to those descriptions made with respect to therespective steps of the methods with reference to FIGS. 3A to 10.

It is further noted that the components of the apparatuses 1100 to 1400may be embodied in hardware, software, firmware, and/or any combinationthereof. For example, the components of apparatuses 1100 to 1400 may berespectively implemented by a circuit, a processor or any otherappropriate selection device. Those skilled in the art will appreciatethat the aforesaid examples are only for illustration not limitation.

In some embodiment of the present disclosure, each of apparatuses 1100to 1400 comprises at least one processor. The at least one processorsuitable for use with embodiments of the present disclosure may include,by way of example, both general and special purpose processors alreadyknown or developed in the future. Each of apparatuses 1100 to 1400further comprises at least one memory. The at least one memory mayinclude, for example, semiconductor memory devices, e.g., RAM, ROM,EPROM, EEPROM, and flash memory devices. The at least one memory may beused to store program of computer executable instructions. The programcan be written in any high-level and/or low-level compliable orinterpretable programming languages. In accordance with embodiments, thecomputer executable instructions may be configured, with the at leastone processor, to cause apparatuses 1100 to 1400 to at least performoperations according to the method as discussed with reference to FIGS.3A, 3B 4A and 4B respectively.

In addition, FIGS. 15A and 15B and FIGS. 16A and 16B further illustratesimulation results made on an embodiment of the present invention andthe existing solution in the prior art. Parameters used in thesimulations are listed in Table 1.

TABLE 1 Parameters used in the simulations Parameter Assumptions usedfor simulation System bandwidth 14 MHz Frame structure FDD or TDD UL-DLconfigurateion 0 Carrier Frequency 2 GHz for FDD/2.6 GHz for TDD Antennaconfiguration 2 × 2, low correlation Channel model EPA, Dopper spread 1Hz MCS 0 Number of DL RBs 6 Transmission mode TM2 Frequency trackingfactor 100 Hz or 0 Hz Performance target 10% iBLER Channel estimationRealistic channel estimation The minimum required SINR −19.3 dB OutputThe amount of repetitions at the minimum required SINR

FIGS. 15A and 15B illustrate simulation results on performance of theredifferent schemes with 0 dB power offset and 3 dB power offset. Thethree schemes include a Rel. 8 CRS based channel estimation, a Rel. 10DMRS based channel estimation as proposed in R1-130237, and a MTCRSbased channel estimation as proposed in the present document. From FIGS.15A and 15B it is clear that the MTCRS based channel estimation asproposed in the present disclosure is always superior to the other twoprior art schemes regardless of 0 dB power offset and 3 dB power offset.This lies in that in the MTCRS based channel estimation, channelestimation is performed based on both the newly introduced MTCRS and thelegacy reference signal, which provides a higher accuracy of channelestimation.

FIGS. 16A and 16B illustrate simulation results on performance of threedifferent schemes with 0 Hz frequency offset and 100 Hz frequencyoffset, wherein the power offset is set as 0 dB. The three schemes aresomewhat different from those in FIGS. 15A and 15B and they include afirst channel estimation scheme based on a single sub-frame chest andRel. 8 CRS, a second channel estimation scheme based on a signalsub-frame chest and MTCRS as proposed in the present invention, and athird estimation channel scheme based on ten sub-frames channelestimation and Rel. 8 CRS.

It is clear that the second channel estimation scheme as proposed in thepresent disclosure could achieve a better performance than the firstchannel estimation scheme both when there is a frequency offset and whenthere is no frequency offset. In a case that they both use a same singlesub-frame Chest, the second channel estimation scheme as proposed in thepresent disclosure could always provide more accuracy and thus requiredrepetition number is much lower.

Additionally, it may be also seen that when there is a frequency offset,the second channel estimation scheme as proposed in the presentdisclosure is also superior to the third channel estimation scheme whichuses ten subframes channel estimation. However, in a case that there isno frequency offset, the third channel estimation achieves a somewhatbetter performance than the second one. This is because the thirdchannel estimation scheme adopts ten sub-frames channel estimation,which can't track the phase error accumulation when the frequency offsetis high. Therefore, it is clear that with the present invention, thoseUEs with a very low SNR (such as MTC UE) may be also used in LTEnetworks and may achieve a good performance.

The skilled in the art may appreciate that downlink/uplink MTCRS patternand mapping given herein are only for a purpose of illustration and manyother alternative pattern may be used with out departing the scope andspirit of the present disclosure.

Additionally, it may also be appreciated that the embodiments of thepresent disclosure are described with reference to MTC, however thepresent invention is not limited thereto and the present invention maybe used any communication with a low SNR in LTE system.

Additionally, based on the above description, the skilled in the artwould appreciate that the present disclosure may be embodied in anapparatus, a method, or a computer program product. In general, thevarious exemplary embodiments may be implemented in hardware or specialpurpose circuits, software, logic or any combination thereof. Forexample, some aspects may be implemented in hardware, while otheraspects may be implemented in firmware or software which may be executedby a controller, microprocessor or other computing device, although thedisclosure is not limited thereto. While various aspects of theexemplary embodiments of this disclosure may be illustrated anddescribed as block diagrams, flowcharts, or using some other pictorialrepresentation, it is well understood that these blocks, apparatus,systems, techniques or methods described herein may be implemented in,as non-limiting examples, hardware, software, firmware, special purposecircuits or logic, general purpose hardware or controller or othercomputing devices, or some combination thereof.

The various blocks shown in the accompanying drawings may be viewed asmethod steps, and/or as operations that result from operation ofcomputer program code, and/or as a plurality of coupled logic circuitelements constructed to carry out the associated function(s). At leastsome aspects of the exemplary embodiments of the disclosures may bepracticed in various components such as integrated circuit chips andmodules, and that the exemplary embodiments of this disclosure may berealized in an apparatus that is embodied as an integrated circuit, FPGAor ASIC that is configurable to operate in accordance with the exemplaryembodiments of the present disclosure.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anydisclosure or of what may be claimed, but rather as descriptions offeatures that may be specific to particular embodiments of particulardisclosures. Certain features that are described in this specificationin the context of separate embodiments can also be implemented incombination in a single embodiment. Conversely, various features thatare described in the context of a single embodiment can also beimplemented in multiple embodiments separately or in any suitablesub-combination. Moreover, although features may be described above asacting in certain combinations and even initially claimed as such, oneor more features from a claimed combination can in some cases be excisedfrom the combination, and the claimed combination may be directed to asub-combination or variation of a sub-combination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various systemcomponents in the embodiments described above should not be understoodas requiring such separation in all embodiments, and it should beunderstood that the described program components and systems cangenerally be integrated together in a single software product orpackaged into multiple software products.

Various modifications, adaptations to the foregoing exemplaryembodiments of this disclosure may become apparent to those skilled inthe relevant arts in view of the foregoing description, when read inconjunction with the accompanying drawings. Any and all modificationswill still fall within the scope of the non-limiting and exemplaryembodiments of this disclosure. Furthermore, other embodiments of thedisclosures set forth herein will come to mind to one skilled in the artto which these embodiments of the disclosure pertain having the benefitof the teachings presented in the foregoing descriptions and theassociated drawings.

Therefore, it is to be understood that the embodiments of the disclosureare not to be limited to the specific embodiments disclosed and thatmodifications and other embodiments are intended to be included withinthe scope of the appended claims. Although specific terms are usedherein, they are used in a generic and descriptive sense only and notfor purposes of limitation.

1. A method for downlink data transmission in a wireless communicationsystem, comprising: transmitting an indication for a new-type referencesignal to a user equipment, wherein the new-type reference signal has anidentical location in frequency domain to a legacy reference signal; andtransmitting the new-type reference signal and the legacy referencesignal to the user equipment for using in channel estimation.
 2. Themethod according to claim 1, wherein the new-type reference signal has adifferent location in time domain from the legacy reference signal. 3.The method according to claim 1, further comprising, determining atransmission repetition number for the user equipment based on signal tonoise ratio; and transmitting the transmission repetition number to theuser equipment.
 4. The method according to claim 1, further comprising,transmitting a power boosting parameter to the user equipment; andwherein the new-type reference signal is transmitted at a boosted powerindicated by the power boosting parameter.
 5. The method according toclaim 1, wherein the new-type reference signal is transmitted when aphysical downlink shared channel resource is scheduled for the userequipment.
 6. The method according to claim 1, wherein the legacyreference signal comprises any one of a cell specific reference signaland a demodulation reference signal.
 7. The method according to claim 1,wherein the method is performed in response to a coverage enhancementindication for the user equipment.
 8. The method according to claim 1,further comprising sending to the user equipment an antenna ports countindicating an antenna port number for transmitting the new-typereference signal and the legacy reference signal.
 9. A method fordownlink data transmission in a wireless communication system,comprising: receiving an indication for a new-type reference signal,wherein the new-type reference signal has an identical location infrequency domain to a legacy reference signal; receiving the new-typereference signal and the legacy reference signal according to theindication; and performing channel estimation based on both the new-typereference signal and the legacy reference signal.
 10. The methodaccording to claim 9, wherein the new-type reference signal has adifferent location in time domain from the legacy reference signal. 11.The method according to claim 9, further comprising: receiving atransmission repetition number; and wherein signal demodulation isperformed based on the transmission repetition number.
 12. The methodaccording to claim 9, further comprising, receiving an antenna portscount that indicates an antenna port number for transmitting thenew-type reference signal and the legacy reference signal; and receivingthe new-type reference signal and the legacy reference signal accordingto the antenna ports count.
 13. The method according to claim 9, whereinthe legacy reference signal for channel estimation comprises any one ofa cell specific reference signal and a demodulation reference signal.14. An apparatus for downlink data transmission in a wirelesscommunication system, comprising: an indication transmission unit,configured to transmit an indication for a new-type reference signal toa user equipment, wherein the new-type reference signal has an identicallocation in frequency domain to a legacy reference signal; and areference signal transmission unit configured to transmit the new-typereference signal and the legacy reference signal to the user equipmentfor using in channel estimation.
 15. The apparatus according to claim14, wherein the new-type reference signal has a different location intime domain from the legacy reference signal.
 16. The apparatusaccording to claim 14, further comprising, a repetition numberdetermination unit configured to determine a transmission repetitionnumber for the user equipment based on signal to noise ratio; and arepetition number transmission unit configured to transmit thetransmission repetition number to the user equipment.
 17. The apparatusaccording to claim 14, wherein the reference signal transmission unit isconfigured to transmit the new-type reference signal when a physicaldownlink shared channel resource is scheduled for the user equipment.18. An apparatus for downlink data transmission in a wirelesscommunication system, comprising: an indication receiving unitconfigured to receive an indication for a new-type reference signal,wherein the new-type reference signal has an identical location infrequency domain to a legacy reference signal; a reference signalreceiving unit configured to receive the new-type reference signal andthe legacy reference signal in according to the indication; and achannel estimation unit configured to perform channel estimation basedon both the new-type reference signal and the legacy reference signal.19. The apparatus according to claim 18, wherein the new-type referencesignal has a different location in time domain from the legacy referencesignal.
 20. The apparatus according to claim 18, further comprising: arepetition number receiving unit configured to receive a transmissionrepetition number; and wherein signal demodulation is performed based onthe transmission repetition number.
 21. A method for uplink datatransmission in a wireless communication system, comprising,transmitting an indication for a new-type reference signal to a userequipment, wherein the new-type reference signal has an identicallocation in frequency domain to a legacy reference signal; receiving thenew-type reference signal and the legacy reference signal from the userequipment; and performing channel estimation based on both the new-typereference signal and the legacy reference signal.
 22. The methodaccording to claim 21, wherein the new-type reference signal has adifferent location in time domain from the legacy reference signal. 23.The method according claim 21, further comprising, determining atransmission repetition number for the user equipment based on signal tonoise ratio; and transmitting the transmission repetition number to theuser equipment.
 24. The method according to claim 21, wherein the methodis performed in response to a coverage enhancement indication for theuser equipment.
 25. The method according to claim 21, wherein the legacyreference signal comprises a demodulation reference signal.
 26. Themethod according to claim 21, further comprising sending to the userequipment an antenna ports count indicating an antenna port number fortransmitting the new-type reference signal and the legacy referencesignal.
 27. A method for uplink data transmission in a wirelesscommunication system, comprising, receiving an indication for a new-typereference signal from a base station, wherein the new-type referencesignal has an identical location in frequency domain to a legacyreference signal; and transmitting the new-type reference signal and thelegacy reference signal to the base station for using in channelestimation.
 28. The method according to claim 27, wherein the new-typereference signal has a different location in time domain from the legacyreference signal.
 29. The method according to claim 27 furthercomprising receiving a transmission repetition number from the basestation so as to transmit signals based thereon.
 30. The methodaccording to claim 27 wherein the new-type reference signal istransmitted when a physical uplink shared channel resource is scheduledfor the user equipment.
 31. The method according to claim 27, whereinthe legacy reference signal for channel estimation comprises ademodulation reference signal.
 32. The method according to claim 27,wherein the method is performed in response to a coverage enhancementindication for the user equipment.
 33. The method according to claim 27,further comprising receiving an antenna ports count that indicates anantenna port number for transmitting the new-type reference signal andthe legacy reference signal; and transmitting the new-type referencesignal and the legacy reference signal according to the antenna portscount.
 34. An apparatus for uplink data transmission in a wirelesscommunication system, comprising, an indication transmission unitconfigured to transmit an indication for a new-type reference signal toa user equipment, wherein the new-type reference signal has an identicallocation in frequency domain to a legacy reference signal; a referencesignal receiving unit configured to receive the new-type referencesignal and the legacy reference signal from the user equipment; and achannel estimation unit configured to perform channel estimation basedon both the new-type reference signal and the legacy reference signal.35. The apparatus according to claim 34, wherein the new-type referencesignal has a different location in time domain from the legacy referencesignal.
 36. The apparatus according claim 34, further comprising, arepetition number determination unit configured to determine atransmission repetition number for the user equipment based on signal tonoise ratio; and a repetition number determination unit configured totransmit the transmission repetition number to the user equipment. 37.An apparatus for uplink data transmission in a wireless communicationsystem, comprising, an indication receiving unit configured to receivean indication for a new-type reference signal from a base station,wherein the new-type reference signal has an identical location infrequency domain to a legacy reference signal; and a reference signaltransmission unit configured to transmit the new-type reference signaland the legacy reference signal to the base station for using in channelestimation.
 38. The apparatus according to claim 37, wherein thenew-type reference signal has a different location in time domain fromthe legacy reference signal.
 39. The apparatus according to claim 37,further comprising a repetition number receiving unit configured toreceive a transmission repetition number from the base station so as totransmit signals based thereon.
 40. The apparatus according to claim 37,wherein the reference signal transmission unit is further configured totransmit the new-type reference signal when a physical uplink sharedchannel resource is scheduled for the user equipment.